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Effects of Mechanical Harvest plus Chipping and Prescribed Fire on Sierran Runoff Water Quality
Author(s) -
Loupe T.M.,
Miller W.W.,
Johnson D.W.,
Sedinger J.S.,
Carroll E.M.,
Walker R.F.,
Murphy J.D.,
Stein C.M.
Publication year - 2009
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2007.0494
Subject(s) - surface runoff , environmental science , nutrient , snowmelt , hydrology (agriculture) , prescribed burn , water quality , leaching (pedology) , growing season , soil science , soil water , agronomy , ecology , geology , biology , geotechnical engineering
Fire suppression in Sierran ecosystems creates a substantial wildfire hazard and may exacerbate nutrient inputs into Lake Tahoe by allowing the buildup of O horizon material, which serves as a source for high N and P concentrations in runoff water. The purpose of this study was to evaluate the effects of biomass reduction using cut‐to‐length mechanical harvest followed by chipping and controlled burning on surface runoff volume and water quality. Based on previous findings regarding N and P leaching flux and soil solution concentrations, we hypothesized that controlled burning and/or mechanical harvest with residue chipping does not increase inorganic N, P, and S concentrations in overland flow. Runoff, snowmelt, and rainfall were collected, volume measurements were taken, and samples were analyzed for NO 3 –N, NH 4 –N, PO 4 –P, and SO 4 Runoff volume, season, and year were identified as important parameters influencing overland flow nutrient concentrations and loads. Higher nutrient concentrations were commonly associated with summer rather than winter runoff, but the opposite was true for nutrient loads due to the higher runoff volumes. Treatment (unharvested, harvested, unburned, burned) effect was a strong predictor for discharge loads of NO 3 –N and SO 4 but was a weak predictor for PO 4 –P. Discharge loads of NO 3 –N and SO 4 were greater for the unburned harvested and the burned unharvested treatments than for the unburned, unharvested control sites or the burned and harvested combined treatment. Although mechanical harvest and/or controlled burning had a small initial impact on increased nutrient loading, the effects were minimal compared with background levels. Hence, these management practices may have the potential to improve forest health without the danger of large‐magnitude nutrient mobilization and degradation of runoff water quality found with wildfire.